From the about page: http://warmingworld.newscientistapps.com/about.html http://warmingworld.newscientistapps.com/about.html "Surface temperature measurements

From the about page: http://warmingworld.newscientistapps.com/about.html http://warmingworld.newscientistapps.com/about.html "Surface temperature measurements are not evenly distributed across the globe. So the NASA team interpolates from the available data to calculate average temperatures for cells in a global grid, with each cell measuring 2 degrees latitude by 2 degrees longitude. The analysis extrapolates up to 1200 kilometres from any one station, which allows for more complete coverage in the Arctic – where monitoring stations are sparsely distributed, but where the warming trend is especially strong."